The U.S. Securities and Exchange Commission and the Department of Justice filed charges on Thursday against a 19-year-old Pennsylvania man accused of using a Trojan horse program to steal money from another man's brokerage account.

The complaints filed in civil court by the SEC and in criminal court by the Justice Department charge Van T. Dinh, a resident of Phoenixville, Penn., of securities fraud and computer crimes. The case is the SEC's first prosecution of a person accused of both computer intrusion and identity fraud.

"This case should remind investors using the Internet to review their brokerage statements carefully every month, to check the bona fides of any potential download and to take security measures," John Reed Stark, chief of the SEC's Office of Internet Enforcement, said in a statement.

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Vinh is accused of persuading an investor in Westborough, Mass., to download a program in July with which the suspect allegedly monitored the victim's computer. Under the name "Tony T. Reichert," Vinh allegedly sent e-mail to the investor and several others met through a stock-discussion site, asking them if they wanted to take part in a beta test of a new stock-charting tool. The tool was actually a Trojan horse program that recorded any text input via the keyboard, according to the complaints. Using the program, Vinh was allegedly able to obtain the account name and password for the investor's online brokerage account. He then proceeded to drain the account of nearly $47,000, the complaints charge.

"This case should be a reminder to Internet users that every time they open an e-mail from an unknown sender, it is as if they are opening the front door of their house to a stranger," Michael Sullivan, U.S. attorney for the District of Massachusetts, said in a statement.

The charges filed by the Justice Department could result in a maximum sentence of 30 years imprisonment and a $1 million fine. The SEC's charges, filed in civil court, ask for all money from the alleged scam to be returned and for unspecified penalties to be paid.